# 8th International Workshop on Multiple Partonic Interactions at the LHC

from 28 November 2016 to 2 December 2016
Hotel Rincón del Arco
Mexico/General timezone
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## Contribution List

Displaying 67 contributions out of 67
Session: WG4
In this talk, I give a review of our work on the exploration of optimal conditions to pin down double parton scattering in four jet production and the LHC in the 7 and 13 TeV data sets, working in the theoretical framework of high energy factorisation. Beside, I elaborate on the first stages of the update of the project, consisting in repeating the investigation by augmenting the theoretical pr ... More
Presented by Dr. Mirko SERINO on 1 Dec 2016 at 15:30
Session: WG4
We obtain a pair of second order differential equations in two variables $x$ and $t$ from the coupled DGLAP QCD evolution equations at small $x$ using the standard Taylor series expansion method.To that end we keep terms upto $O(x^2)$.We use the standard assumption about the relationship between the singlet Structure Function and the gluon distributions available in current literature. We then sh ... More
Presented by Ms. Luxmi MACHAHARI
Session: WG4
The ATLAS collaboration has carried out a study of diffractive dijet production at 7 TeV pp collisions at the LHC, i.e. events with a hadronic system containing at least two jets in addition to a large region of pseudorapidity devoid of hadronic activity. The data distributions are compared with Monte Carlo models and the rapidity gap survival probability has been estimated in the kinematic re ... More
Presented by Dr. Marek TASEVSKY on 1 Dec 2016 at 09:20
Session: WG3
The ATLAS collaboration has carried out several analyses that are sensitive to hard Double Parton Scattering (DPS). A review of recent results is given. These include the final results of a study of DPS in events with four jets, where uncertainties on the effective DPS cross section are improved compared to preliminary results and differential unfolded distributions are measured, that are sens ... More
Presented by Ewelina LOBODZINSKA on 2 Dec 2016 at 18:30
Session: WG5
ATLAS measurements of correlations between particle pairs in relative azimuthal angle ($\Delta\phi$) and pseudorapidity separation ($\Delta\eta$), in $pp$ collisions at $\sqrt{s}$=2.76, 5.02 and 13~TeV, and in $p$+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$=5.02~TeV are presented. Prior measurements have shown that in $pp$ collisions with a large multiplicity of produced particles, a long-rang ... More
Presented by Dr. Deepak KAR on 1 Dec 2016 at 12:10
Session: WG3
Abstract -------- In [1] Gaunt and Stirling proposed a set of momentum and quark number sum rules, in close analogy to the well known PDF sum rules, that sensible, transverse momentum integrated, double parton distributions (DPDs) should obey. In their work they argued that these sum rules hold under LO QCD evolution, if one assumes that they are fulfilled at the starting scale. While Gaunt an ... More
Presented by Mr. Peter PLÖßL on 2 Dec 2016 at 18:10
Session: WG4
We present a complete Monte Carlo program for automatic calculations of hard single- and multi-parton scattering processes within collinear- and k_T-factorization. It can use any k_T-dependent pdfs in the form of a grid file, and collinear pdfs from LHAPDF. It provides all tree-level matrix elements for any processes within the standard model and includes efficient phase space generators. It produ ... More
Presented by Andreas VAN HAMEREN on 1 Dec 2016 at 14:30
Session: WG2
We combine the IP-Glasma model of Color Glass Condensate with PYTHIA to study bulk observables in small colliding systems at LHC. This framework combines the Classical Yang-Mills dynamics of multi-gluon productions and a scheme of fragmentation based on Lund string model for the production of hadrons. In particular we study the high multiplicity events in which observations are often attributed to ... More
Presented by Prithwish TRIBEDY on 29 Nov 2016 at 15:00
Session: WG1
Different distributions of charged-particles and leading charged-particle produced in proton-proton collisions at a centre-of-mass energy $\sqrt{s} = 13$ TeV are measured in the pseudorapidity range $|\eta| < 2.4$ for charged-particles with a transverse momentum $p_T~>~0.5$ GeV. Measurements are presented for four event categories. The first two categories correspond to inclusive and inelastic e ... More
Presented by Mr. Juan Manuel GRADOS LUYANDO on 28 Nov 2016 at 12:00
Session: WG5
The centrality-dependence of forward jet production in \pA\ collisions at the LHC has been found to grossly violate the Glauber model prediction in a way that depends on the $x$ in the proton. We argue that this modification pattern provides the first experimental evidence for $x$-dependent proton color fluctuation effects. On average, parton configurations in the projectile proton cont ... More
Presented by Prof. Mark STRIKMAN on 28 Nov 2016 at 17:40
Session: WG2
The DPMJET-III Monte Carlo event generator models interactions of hadrons, nuclei and photons with energies above a few GeV up to the highest cosmic ray energies. The photon-photon, photon-hadron and hadron-hadron part relies on a new version of the PHOJET Monte Carlo, that has been recently updated with new parton densities, the support for various baryon and meson projectiles and retuned paramet ... More
Presented by Anatoli FEDYNITCH on 29 Nov 2016 at 11:20
Session: WG3
We present recent results on Double Parton Scattering (DPS) studies using data collected during Run 1 and Run 2 of the LHC with the CMS experiment. Double parton scattering is investigated in several final states including vector bosons and multi-jets. Measurements of observables designed to highlight the DPS contribution are shown and compared to MC predictions from models based on multiple parto ... More
Presented by Mr. Ramandeep KUMAR
Session: WG5
Our understanding of proton structure and of nuclear interactions at high energy would be advanced significantly with the definitive discovery of the gluon saturation regime. Forward particle production in hadron collisions at RHIC probes gluons at small-x where gluon density is high and expected to reach the saturation regime. Until today the golden channel at RHIC to observe strong hints of satu ... More
Presented by akio OGAWA
Session: WG3
We give an update on a consistent scheme to separate single from double hard scattering, as introduced at last year's MPI@LHC. In particular, several new numerical results will be presented to illustrate the working of the scheme.
Presented by Dr. Jonathan GAUNT on 29 Nov 2016 at 17:00
Session: WG1
Recent measurements, performed with the CMS and TOTEM experiments, of the elastic and inelastic cross section are presented and compared. The inelastic cross section at 13 TeV is measured with CMS in two fiducial regions using information from forward calorimetry, and finally extrapolated to the full inelastic phase space.
Presented by Kumar RAMANDEEP, Juan Manuel GRADOS LUYANDO on 1 Dec 2016 at 17:00
Session: WG5
In this contribution, we report on the multiplicity dependence of strange and multi- strange hadron production in pp collisions at √sNN = 5.02 TeV with the ALICE experiment. An enhanced production of strange and multi-strange hadrons relative to pions is observed for pp and p-Pb collisions where a large charged-particle multiplicity density is reached. The results in small systems are compared ... More
Presented by Prabhakar PALNI on 28 Nov 2016 at 16:30
Session: WG4
The installation of scintillating pad detectors (Herschel), bracketing the LHCb detector along the beamline, have significantly enhanced the LHCb sensitivity to central exclusive production. Additionally, dedicated triggers during the early measurement period of Run 2 produced an extended CEP dataset. A summary of results from Run 1 as well as early results from Run 2 will be shown.
Presented by Philip ILTEN on 1 Dec 2016 at 10:20
Session: WG4
MPI models implemented in Monte Carlo generators typically rely on the minijet cross section formula derived from the LO collinear factorization supplemented with a $p_T$ cutoff, which slowly grows with the energy. The natural question is whether such a cutoff can be explained (or dynamically generated) from an approach which goes beyond the leading power. One of approaches venturing beyond the le ... More
Presented by Piotr KOTKO on 1 Dec 2016 at 15:50
Session: WG4
The measurements of diffractive dijet and open charm ep cross sections in deep-inelastic scattering and photoproduction at HERA will be discussed with an emphasis on possible QCD factorisation breaking.
Presented by Dr. Alice VALKAROVA on 1 Dec 2016 at 10:40
Session: WG5
The talk will review the results recently reported by the CMS experiment on the study of light flavour and production of strangeness versus multiplicity in small systems
Presented by Valentina MARIANI on 28 Nov 2016 at 15:50
Session: WG4
Measurements on the forward energy flow using the HF and CASTOR calorimeters are presented together with a first measurement of very low pT jets in a pseudorapidity region of -6.6 < eta < -5.2 in pp collisions at a centre-of-mass energy of 13 TeV.
Presented by Collaboration CMS
Session: WG4
We discuss diffractive production of open charm and bottom mesons and dijet at the LHC. The differential cross sections for single- and central-diffractive mechanisms for $c \bar c$and $b \bar b$ pair production and dijets are calculated in the framework of the Ingelman-Schlein model corrected for absorption effects. In this approach one assumes that the pomeron has a well defined partonic stru ... More
Presented by Dr. Marta LUSZCZAK on 1 Dec 2016 at 16:10
Session: WG1
Presented by Dr. Deepak KAR
Session: WG1
Presented by Dr. Deepak KAR on 28 Nov 2016 at 10:00
Session: WG2
on 29 Nov 2016 at 09:00
Session: WG3
on 29 Nov 2016 at 15:20
Session: WG4
on 1 Dec 2016 at 09:00
Session: WG5
on 28 Nov 2016 at 15:00
Session: WG4
ATLAS has no new dedicated analyses on BFKLtype analyses. We suggest the following mixture of jet veto / exclusive jet cross sections in V+jet, VV+jet, multijets: - Z+jets 13 TeV and Jet vetoes in Z VBF, W VBF studies - WW+0,1 jets http://arxiv.org/abs/1608.03086 - Other dibosons + jets: Zgamma+jets and WZ+jets http://arxiv.org/abs/1606.04017,http://arxiv.org/abs/1604.05232 - Studies of ra ... More
Presented by Gavin Grant HESKETH on 1 Dec 2016 at 10:00
Session: WG5
Two-particle angular correlations are studied in proton-lead collisions at a nucleon-nucleon centre-of-mass energy of 5TeV, collected with the LHCb detector at the LHC. The analysis is based on data recorded in two opposing beam configurations, in which either the direction of the proton or that of the lead remnant is analysed. The correlations are measured as a function of relative pseudorapidity ... More
Presented by Prof. Zhu XIANGLEI on 1 Dec 2016 at 12:30
Session: WG2
During the last years collective effects in small systems, like p-p and p-A, have been under discussion. Evidence of flow-like patterns has been found in p-p collisions experimentally. Based on this results the proposal to use hydrodynamics to describe small systems, like in A-A collisions, looks tempting, but, some other mechanisms, among them prominently, Color Reconnection (CR), has shown colle ... More
Presented by Sergio IGA on 1 Dec 2016 at 11:50
Session: WG5
We study the multiparton interaction dependence of the mean pT fluctuations for isotropic (soft) and jetty-like (hard) events with PYTHIA 8 for p-p collisions at .9, 2.76,7, 13 TeV for different pT intervals. Results are compared with published data at the LHC on corresponding multiplicity intervals, as well as with other models with different nature like EPOS and the String Percolation. The resul ... More
Presented by Dr. irais BAUTISTA on 1 Dec 2016 at 12:50
Session: WG3
At transverse momenta that are large compared with nonperturbative scales but much smaller than the hardest scale in the process, DPS can be described by TMD factorisation with transverse-momentum dependent DPDs computed in terms of collinear ones. We describe the formalism and main results of this procedure for double Drell-Yan and double Higgs production, generalising the well-known results for ... More
Presented by Tomas KASEMETS on 29 Nov 2016 at 17:40
Session: WG1
The modelling of Minimum Bias (MB) is a crucial ingredient to learn about the description of soft QCD processes. It has also a significant relevance for the simulation of the environment at the LHC with many concurrent pp interactions (“pileup”). The ATLAS collaboration has provided new measurements of the inclusive charged particle multiplicity and its dependence on transverse momentum ... More
Presented by Jiri KVITA on 28 Nov 2016 at 11:40
Session: WG1
The modelling of the Underlying Event (UE) is a crucial component in the complete description of both soft and hard QCD processes at hadron colliders. The ATLAS collaboration presents new results on the number and transversemomentum sum of charged particles as a function of the leading high pT track in events taken at a center of mass energy of 13 TeV. These results are presented in regions t ... More
Presented by Robert ASTALOS on 28 Nov 2016 at 10:30
Session: WG3
Measurements of the differential cross sections for the production of at least four jets, two of them initiated by b-quarks, in proton-proton collisions are presented as a function of the transverse momentum pt and pseudorapidity eta, together with the correlations in azimuthal angle and the pt balance among the jets. The data sample was collected in 2010 at a center-of-mass energy of 7 TeV with t ... More
Presented by Paolo GUNNELLINI on 29 Nov 2016 at 16:10
Session: WG5
We report the latest results of relative J/psi yield versus charged-particle multiplicity at mid-rapidity in p+p collisions at sqrt(s)=200 GeV with the STAR experiment. The measured J/psi yields and charged-particle multiplicities have been corrected for STAR detector acceptance and efficiency, and are compared to results from LHC experiments as well as theoretical calculations based on phenomen ... More
Presented by Prof. Zhenyu YE on 28 Nov 2016 at 18:00
Session: WG2
Monte Carlo event generators used at LHC are inspired by QCD and rely on phenomenological models where perturbative QCD cannot be used, e.g. for the description of the underlying event and hadronisation. This requires experimental data to constrain and tune the models, and to ultimately gain insights in the underlying physics. A Large Ion Collider Experiment (ALICE) at the LHC provides trac ... More
Presented by Dr. Jochen KLEIN on 29 Nov 2016 at 09:30
Session: WG2
The primary emphasis will be on proton-(anti)proton collisions, but can also heavy ion results related to Monte-Carlo studies.
Presented by Paolo GUNNELLINI on 29 Nov 2016 at 12:00
Session: WG2
The modelling of Minimum Bias (MB) and Underlying Event (UE) is a crucial component in the description of soft QCD processes. They are both described by multi-parton interactions (MPI) models, the result of proton collisions containing more than one partonic interaction due to collective and beam remnant effects. We present recent ATLAS studies aimed at improving the description of MPI models i ... More
Presented by Valentina Maria CAIRO on 29 Nov 2016 at 10:10
Session: WG4
Mueller Navelet dijet measurements in pp collisions at a centre-of-mass energy of 7 TeV are presented. This includes azimuthal decorrelations and their average cosines. In addition, new measurements of the exclusive to inclusive (MN) dijet cross section ratios are presented at a centre-of-mass energy of 2.76 TeV.
Presented by Collaboration CMS
Session: WG5
Recent measurements of Bose-Einstein correlations in pp, pPb and PbPb collisions are presented at different centre-of-mass energies of 0.9, 2.76, 5.02, 7 and 13 TeV.
Presented by Collaboration CMS
Session: WG2
I'll discuss the treatment of multiparton interactions in the framework of the QGSJET-II model. A particular attention will be paid to the assumptions concerning the momentum structure of constituent parton Fock states in hadrons and to the respective consequences for the predicted spectra of secondary hadrons. An impact on the predictions for cosmic-ray induced extensive air showers will be also ... More
Presented by Dr. Sergey OSTAPCHENKO on 29 Nov 2016 at 11:40
Session: WG5
Recent measurements performed in high-multiplicity proton-proton (pp) and proton-lead (p-Pb) collisions have revealed features that are reminiscent of lead-lead (Pb-Pb) phenomenology. The investigation of such phenomena requires a systematic study of light-flavor particle production as a function of charged particle multiplicity. ALICE has unique PID capabilities at mid-rapidity and excel ... More
Presented by Dr. Stefania BUFALINO on 28 Nov 2016 at 15:30
Session: WG2
Sibyll is one of the hadronic event generators commonly used in the simulation of extensive air showers. Since the last release, which dates back to the TeVatron era, modeling of hadronic interactions has seen development in several directions. For one the high energy frontier has been significantly moved up by the LHC, revealing discrepancies in the prediction of the total cross section, the ... More
Presented by Felix RIEHN on 29 Nov 2016 at 12:20
Session: WG3
We calculate the rate of double open charm production in the forward kinematics studied recently in the LHCb experiment. We find that the mean field approximation for the double parton GPD (Generalized parton distributions), which neglects parton - parton correlations, underestimates the rate by a factor of two. The enhancement due to the perturbative QCD correlation 1->2 mechanism which exp ... More
Presented by Prof. Mark STRIKMAN on 30 Nov 2016 at 18:20
Session: WG5
Open and hidden heavy flavour production measurements in proton-proton (pp) collisions at the Large Hadron Collider (LHC) provide a test for perturbative Quantum Chromodynamics (pQCD) inspired models. In particular, the correlation of the heavy-flavour hadron yields with charged particles produced in hadronic collisions can shed light on their production mechanism and on the interplay between hard ... More
Presented by Dr. Lizardo VALENCIA PALOMO on 28 Nov 2016 at 18:20
Session: WG3
We present recent studies on the effects of different kind of correlations in double parton distribution functions (dPDFs). These quantities have been calculated in Ref. [1], within the Light-Front fully Poincar\'e covariant approach and in a constituent quark model framework. This first analysis shows how dynamical correlations, induced by the used model, prevent the factorization o ... More
Presented by Dr. Matteo RINALDI on 1 Dec 2016 at 17:50
Session: WG4
Status of the AFP project in the ATLAS experiment is given. In 2016 one arm of the AFP detector was installed and first data have been taken. In parallel with integration of the AFP subdetector into the ATLAS TDAQ nad DCS, beam tests and preparations for the installation of the 2nd arm are performed.
Presented by Grzegorz Pawel GACH on 1 Dec 2016 at 09:40
Session: WG1
We present results on the measurement of the underlying event at 13 TeV using leading tracks, jets, and Drell-Yan processes. In addition measurements of forward-backward particle correlations and the rapidity gap fraction are presented. Finally results on charged particle multiplicity and transverse momenta distributions are shown.
Presented by Mr. Juan Manuel GRADOS LUYANDO on 28 Nov 2016 at 12:20
Session: WG4
In this talk we will give the most recent results from TOTEM concerning elastic and total cross section. We will also describe the CMS-TOTEM/Precision Proton Spectrometer (CT-PPS) project in order to take diffractive and photon induced processes at the LHC also at high luminosities. We will present briefly the detector and the physics that can be performed.
Presented by Prof. Christophe ROYON on 1 Dec 2016 at 15:10
Session: WG3
Double parton scattering (DPS) is highly intriguing since it can provide information on parton transverse profile and parton-parton correlations within a proton. During the LHC Run-I period, DPS is actively explored at LHCb via double $J/\psi$, double charmed hadrons, $\Upsilon$ plus open charm processes. The recent results from LHCb will be presented, including the measurement of double $J/\psi$ ... More
Presented by Ms. An LIUPAN on 29 Nov 2016 at 15:50
Session: WG4
An overview of recent diffractive and exclusive measurements with CMS is given. Results on jet-gap-jet event topologies are shown, together with central exclusive pi-pi production at 7 TeV. Diffractive dijet production is measured with proton tagging in pp collisions at 8 TeV. In addition, recent results on exclusive rho0 and upsilon production in pPb collisions at 5.02 TeV are presented.
Presented by Collaboration CMS
Session: WG5
In this work, we propose a tool to reveal the origin of the collective-like phenomena observed in proton-proton collisions. We exploit the fundamental difference between the underlying mechanisms, color reconnection (CR) and hydrodynamics, which produce radial flow patterns in PYTHIA 8 and EPOS 3, respectively. Namely, the strength of the coupling between the soft and hard components which by cons ... More
Presented by Mr. Gyula BENCEDI on 28 Nov 2016 at 16:10
Session: WG2
EPOS3 is a minimum bias Monte-Carlo event generator used for Heavy Ion Collisions. It is successful in the description of particle spectra as well as flow-like observables and includes viscous hydrodynamics expansion, hadronic cascade, and heavy quark production. In the beginning, we will present the general features of the model and show that multiple interactions play a central role for both ... More
Presented by Dr. Benjamin GUIOT on 29 Nov 2016 at 10:30
Session: WG3
Soft gluon exchange is an essential part of the dynamics in DPS processes. In processes where factorisation holds, the effects of this exchange are described by soft factors, which give rise to Sudakov logarithms. We discuss progress made in the understanding of the colour dependence of these factors. This leads to significant simplifications both in collinear and in TMD factorisation for D ... More
Presented by Dr. Markus DIEHL, Tomas KASEMETS on 29 Nov 2016 at 17:20
Session: WG2
We discuss soft interactions as part of the Multiple Partonic Interaction model in the Monte Carlo event generator Herwig. The model for soft interactions has been updated and complemented with a model for diffractive final states. We describe the model and present simulation results in comparison to data from minimum bias interactions at the LHC.
Presented by Stefan GIESEKE on 29 Nov 2016 at 12:40
Session: WG3
In this presentation we discuss some new aspects of double parton scattering in $p p \to c \bar c c \bar c X$ and $p p \to c \bar c jet jet X$. For double $c \bar c$ production we consider rather production of charmed mesons, each of them containing quark $c$ or each of them containg antiquark $\bar c$. Results of two different models are compared. In one of them the D mesons are produced in ... More
Presented by Prof. Antoni SZCZUREK on 30 Nov 2016 at 18:00
Session: WG3
Same-sign W boson pair production is one of the most promising channels for measuring properties of double parton scattering (DPS) at the LHC. This process has the advantage that the single parton scattering contribution at the same order is forbidden in the Standard Model. The different correlations can have an impact on the size of the DPS cross-section and significantly alter the distributions ... More
Presented by Ms. Sabrina COTOGNO
Session: WG5
High energy heavy ion collisions resulting in the production of Quark Gluon Plasma (QGP) provide an experimental system where the effects of multiple partonic interactions (MPI) can be studied. Small heavy ion systems such as d+Au collisions are of particular relevance to studying MPI because MPI effects can be better isolated. We can examine to what degree MPI plays a role in the initial collisio ... More
Presented by Theodore KOBLESKY on 28 Nov 2016 at 17:20
Session: WG1
Presented by Dr. Deepak KAR on 1 Dec 2016 at 17:20
Session: WG1
By measuring the substructure of a jet, one can assign it a quark or gluon tag. In this talk, we confront the challenges faced when going beyond this leading-order understanding, using both parton shower generators and first-principles calculations to assess the impact of higher-order perturbative and nonperturbative physics. Working in the idealized context of electron-positron collisions,where ... More
Presented by Dr. Deepak KAR on 28 Nov 2016 at 12:40
Session: WG2
The forward-backward multiplicity correlations are important for the overall event characterization and to extract information on non-pertubative hadronic processes. In this work we present a study of this correlations based on p+p collisions generated with PYTHIA event generator at LHC energies with different initial conditions of the events to show how it is related with the hadronization mec ... More
Presented by Mr. Edgar DOMINGUEZ ROSAS on 1 Dec 2016 at 11:30
Session: WG4
In this talk we present the key tools developed in a study of QCD dynamics at small x, through hadron azimuthal angular correlations. We calculate the triple differential cross section for inclusive production of three polarized partons in DIS at small x, where the target proton or nucleus is described using the Color Glass Condensate (CGC) formalism. Furthermore, we discuss how our analytic expre ... More
Presented by Dr. Maria Elena TEJEDA-YEOMANS
Session: WG4
The total pp cross section is a fundamental property of the strong interaction which can not be calculated in perturbative QCD but only described based on phenomenological models. The ATLAS collaboration has recently measured the total inelastic protonproton cross section and the diffractive part of the inelastic cross section at 13 TeV in special data sets taken with low beam currents and us ... More
Presented by Christian HEINZ on 1 Dec 2016 at 14:50
Session: WG2
The wealth of data collected by LHCb during Run~I has allowed obtaining a wide selection of results in the unique phase space covered by its detector: pseudorapidity ($\eta$) range $2<\eta<5,$ low $p_T$ and low Bjorken $x$ values. These results are and will be used as reference in the tuning of Monte Carlo generators parameters influencing processes including but not limited to light and heavy qua ... More
Presented by Dr. Marco ADINOLFI on 29 Nov 2016 at 09:50
Session: WG1
Underlying-event activity is defined as the soft particle production in proton+proton collisions which is not directly related to the final fragmentation of hard-scattered partons. Underlying-event measurements therefore provide a tool to study non-factorizable and non-perturbative phenomena. Systematic measurements of the relationship between the underlying event and jet processes provide a cruci ... More
Presented by Dr. Li YI on 28 Nov 2016 at 11:20